What Is Analogue Synthesis?

As a raft of new, affordable analogue synths arrive in 2013, we ask ‘what is analogue synthesis?’

There has been something of an analogue synthesis renaissance in 2013. Despite being barely 3 months into the year, we’ve already been treated to a tempting selection of high quality analogue instruments.

Younger players, and those who are not ‘synth buffs’ might wonder what all the fuss is about. To help, here’s an explanation of what analogue synthesis is, and why it’s so desirable.

In a land before time…

Though the heyday of the analogue synthesizer was arguably the period between the ‘70s and the ‘80s, the earliest analogue synths were developed as early as the ‘20s and ‘30s- and incredibly short period after the development of Alternating Current in the latter part of the 19th century.

Put very simply, an analogue synthesizer is a musical instrument that uses analogue electrical circuits to via AC current to generate sound. This electrical signal is passed through various controllable modifiers, which allow the use to shape the resulting sound according to their needs.

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This is in contrast to modern digital synthesis that employs digital technology, using computer processors running mathematical programs to generate tone (but also with modifiers to shape the sound).

Many of the synthesizers from the early ‘golden era’ of analogue synthesizers were based on the concept subtractive synthesis. It is this concept that the majority of synthesisers are based today.

How does it work? The signal path is as follows…

The Oscillator

Despite its rather complex sounding name, the Oscillator can be thought of simply as the basic sound generator. Electrical components within the synth generate simple, but usually harmonically rich waveforms. Without getting too bogged down in technicality, this consists of the fundamental harmonic (the ‘pitch’ of a note), and many other complementary frequencies with a mathematical relationship to the fundamental harmonic.

The most common of these are sawtooth waves, triangle waves, square waves, and when at its most simple, sine waves. The reason for using harmonically rich is that it provides the ability to exaggerate or cut harmonics from the sound.

LFO – Low frequency oscillator

The LFO can often appear at this point in the signal chain (but it can be used to control aspects of an analogue synthesizer’s sound further down the signal path). An LFO is a modifier that allows the o0scillator to be modified according to a simple, low frequency waveshape (sine, square, saw etc.), usually with the ability to adjust wave depth (amplitude) or speed (frequency).

If used at this point, it would most likely be used to modulate pitch (most commonly via a modulation wheel). If employed elsewhere in the signal path, LFOs can modulate everything from volume, to filter and other parameters.

Filter

Most commonly, the signal will then pass through a filter. This, as the name suggests, allows the user to filter out certain frequencies of the synth sound. There are many varieties of filter, but the most common are Low Pass, High Pass, Band Pass and Notch.

Usually, there are two controls: filter cutoff frequency (this sets the frequency at which the filter will begin to work) and resonance (which controls the amount the sound is ‘boosted’ at the cutoff frequency).

Low pass is the most common type, and allows low frequencies past. The high pass (you guessed it) lets high frequencies past. Band pass is a sort of combination of both high pass and low pass, leaving a frequency band in the middle. A notch filter is almost the inverse of this, providing a notched ‘cut’ at a selected frequency.

Voltage controlled amplifier and envelope

Then, the signal moves onto a crucial section of its signal path: the Voltage Controlled Amplifier (VCA), and usually, the amplifier envelope. This allows you to control the level of the sound in creative ways.

Most simply, the overall amplitude of the sound can be set. The envelope allows the user to shape the amplitude at various points of its development, via attack, decay, sustain and release controls.

Attack sets the length of time it takes for the sound fade in, or to get to full amplitude from silence when the key is pressed.

Decay is the length of time taken to drop from full amplitude to the sustain level.

Sustain is the level at which the sound will play when the note is held.

Release is the length of time it will take for the note to fade to silence from the sustain level after the note is released.

Modifier Envelopes

Usually, an analogue synthesizer will have at least one modifier envelope. This follows the same attack, sustain, decay, release format as above, but is assigned to control another analogue synthesis parameter (filter or modulation, for example).

The signal is then passed out to an audio output, where it can be heard via an amplifier.

Some of you may have noticed that this format is used on many (most) digital synthesizers too, which begs the question ‘what makes analogue synthesizers so great’.

Why analogue synthesis is great

Analogue synthesis is very similar to tube-based guitar amplification in many ways. Both are based on archaic analogue technology, which is less reliable and more expensive than a modern equivalent. So why use it?

It all boils down to quality of sound. Analogue synthesizers are renowned for the warmth of their tone. Try any of 2013’s new analogue synths (MS20 Mini, Bass Station II, Korg Volca Synths), and you’ll hear exactly what we’re talking about. The sound has richness, fullness and ‘size’ that are just about impossible to recreate in any other way.

The other key factor is tonal character. Digital synthesizers are simply running a mathematical program. As a result, they will only ever produce sounds that are within the parameters of the program.

Analogue synthesis is operating within the realms of electrical current, and as a result, has the potential to be far less predictable (in a good way).

Think of it a bit like analogue tape versus digital recording. If you record digitally, but push the levels outside of the device’s dynamic range, you’ll get a horrendous sounding clipping effect.

Push the level on tape, and all sorts of wonderful compression and distortion effects start to happen.

Yes, they can be awkward, and you certainly won’t be getting loads of notes of polyphony or multi-timbrality like you might with a digital synth.

What you will get, however, is tone that you cannot get any other way, and instrument that is inspiring to play and program, due to its unique sonic character. And, with the inclusion of some digital additions, analogue synths no longer drift out of tune in the same way they used to, and have MIDI and USB connections so that they can be easily integrated into a typical studio setup.